Echo intensity compensation by echolocating bats.

When mounted on a swinging pendulum, mustache bats, Pteronotus p. parnellii, emit ultrasonic pulses as they move toward and away from fixed targets. During forward swings they systematically decrease the intensity of their emitted pulses and during backward swings they increase the intensity. In this way, echo strength is continuously adjusted and apparently optimized for signal analysis. We have called this behavior echo intensity compensation. Pteronotus simultaneously Doppler and echo intensity compensate during forward swings of the pendulum but during backward swings they only echo intensity compensate. Pteronotus can regulate the intensity of both the constant frequency and frequency modulated components of their pulses; this regulation is independent of vestibular cues, pulse repetition rates, pulse durations and pulse-echo intervals.